In the journal Nanotechnology, he stresses that tiny machines would need close control in order to be efficient.

Dr Drexler says when he made the statement in the 80s, he underestimated the impact it would have on the field.

Nanotechnology is an umbrella discipline concerned with engineering objects and working devices from individual atoms and molecules.

Bug swarms

"What I did not expect was that efforts to quiet concerns over grey goo would lead to false scientific denials of feasible technologies," Dr Drexler, chairman emeritus of the Foresight Institute in Palo Alto, US, told BBC News Online.

"I also underestimated the popularity of depictions of swarms of tiny nanobugs in science fiction and popular culture."